There has long been a demand for high-speed and high-precision machining, and also in tapping, high-speed and high-precision machining is strongly demanded. For high-speed and high-precision tapping, synchronous tapping has been performed by synchronizing the main spindle with the feed shaft, and various proposals have been made as a method for improving the accuracy and the speed of the synchronous tapping.
As an example of a numerical control device that performs tapping, a numerical control device has been disclosed in which an acceleration/deceleration time constant is determined in accordance with the pitch of thread and a peripheral speed, so that an overshoot of the main spindle during high-speed rotation can be avoided and the machining time during low-speed rotation can be shortened (refer to Patent Document 1).